Prior practices for the fixing of a graphite electrode blank at the end of an electrode holding shank, such as a Model 3R-322/50 shank, available from System 3R USA, Inc., Pompton Plains, N.J., have included gluing or press fitting of the electrode blank onto the shank, bolting the electrode blank onto the shank, and securing the electrode blank onto the shank with screws. These practices are time-consuming and may not always assure a proper mounting of the electrode blank on the shank.
After mounting of the electrode blank on the shank, the shank is mounted in a clamping device, such as a Mini-Block, available from System 3R USA, Inc., Pompton Plains, N.J. The electrode blank is then machined to a desired electrode shape for electrical discharge machining.
Additional methods of mounting an electrode blank on an electrode holder are disclosed in U.S. Pat. Nos. 3,796,852 to Vlach; 4,713,515 to Choi; 4,654,498 to Sato; 3,855,442 to Check et al.; 4,013,862 to O'Connor; 4,020,313 to Koga et al.; and 4,449,027 to Fujikawa.
The Vlach patent discloses a method and apparatus for machining a cavity within a workpiece by electrical discharge machining with a tool having a replaceable electrode tip. The tool includes a positioning member, a holder, a stem attached to the holder, and a tip secured to the stem. During EDM, which produces a cavity, the tip erodes and becomes worn, necessitating replacement. When the electrode tip has become worn, the stem and holder are moved away from the workpiece to permit replacement of the worn tip with a new tip. While the tip is being replaced, the alignment of the stem with respect to the workpiece remains unchanged, and the new tip is automatically aligned with the partial cavity already machined. The tip of the stem includes a split extension which receives a tapered set screw to force the two elements of the split extension to extend laterally. During lateral movement, the elements of the split extension bear against the sides of a central portion of the tip and secures the tip to the split extension.